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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_001_014_2182">&nbsp;</a>NAME</h4><blockquote>
tail - copy the last part of a file
</blockquote><h4><a name = "tag_001_014_2183">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

tail <b>[</b>-f<b>][</b> -c <i>number</i>| -n <i>number</i><b>] [</b><i>file</i><b>]</b>

tail -<b>[</b><i>number</i><b>][</b>b|c|l<b>][</b>f<b>] [</b><i>file</i><b>]</b>

tail +<b>[</b><i>number</i><b>][</b>b|c|l<b>][</b>f<b>] [</b><i>file</i><b>]</b>
</code>
</pre>
</blockquote><h4><a name = "tag_001_014_2184">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>tail</i>
utility copies its input file to the standard output beginning
at a designated place.
<p>
Copying begins at the point in the file indicated by the
<b>-c</b>&nbsp;<i>number</i>
or
<b>-n</b>&nbsp;<i>number</i>
options
(or the &plusmn;
<i>number</i>
portion of the argument to the obsolescent version).
The option-argument
<i>number</i>
is counted in units of lines or bytes,
according to the options
<b>-n</b>
and
<b>-c</b>
(or, in the obsolescent version, the
appended option suffixes
l
(lines),
b
(512-byte blocks)
or
c
(bytes)).
Both line and byte counts start from 1.
<p>
Tails relative to the end of the file
may be saved in an internal buffer, and thus
may be limited in length.
Such a buffer,
if any, will be no smaller than
{LINE_MAX}*10
bytes.
</blockquote><h4><a name = "tag_001_014_2185">&nbsp;</a>OPTIONS</h4><blockquote>
The
<i>tail</i>
utility supports the <b>XBD</b> specification, <a href="../xbd/utilconv.html#usg"><b>Utility Syntax Guidelines</b>&nbsp;</a> ,
except that the obsolescent version accepts multi-character
options that can preceded by a plus sign.
<p>
The following options are supported:
<dl compact>

<dt><b>-c&nbsp;</b><i>number</i>
<dd>
The
<i>number</i>
option-argument must be a decimal integer whose sign
affects the location in the file,
measured in bytes, to begin the copying:
<pre>
<table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Sign</b>
<th align=center><b>Copying Starts</b>
<tr valign=top><td align=center><b>+</b>
<td align=left>Relative to the beginning of the file.
<tr valign=top><td align=center><b>-</b>
<td align=left>Relative to the end of the file.
<tr valign=top><td align=center><b><i>none</i></b>
<td align=left>Relative to the end of the file.
</table>
</pre>

The origin for counting is 1;
that is,
<b>-c +1</b>
represents the first byte of the file,
<b>-c -1</b>
the last.

<dt><b>-f</b>
<dd>If the input file is a regular file or if the
<i>file</i>
operand specifies a FIFO,
do not terminate after the last line of the input
file has been copied, but read and copy
further bytes from the input file when they become available.
If no
<i>file</i>
operand is specified
and standard input is a pipe, the
<b>-f</b>
option will be ignored.
If the input file is not a FIFO, pipe or regular file, it is
unspecified whether or not the
<b>-f</b>
option will be ignored.

<dt><b>-n&nbsp;</b><i>number</i>
<dd>
This option is equivalent to
<b>-c</b>&nbsp;<i>number</i>,
except the starting location in
the file is measured in lines instead of bytes.
The origin for counting is 1;
that is,
<b>-n +1</b>
represents the first line of the file,
<b>-n -1</b>
the last.

</dl>
<p>
In the non-obsolescent form, if neither
<b>-c</b>
nor
<b>-n</b>
is specified,
<b>-n 10</b>
is assumed.
<p>
In the obsolescent version, an argument beginning with a "-" or "+"
can be used as a single option.
The argument
<i>&plusmn;number</i>
with the letter
c
specified as a suffix is equivalent to
<b>-c</b>&nbsp;<i>&plusmn;number</i>;
<i>&plusmn;number</i>
with the
b
suffix is equivalent to
<b>-c</b>&nbsp;<i>&plusmn;number</i>*512;
<i>&plusmn;number</i>
with the letter
l
specified as a suffix, or with none of
b,
c
nor
l
as a suffix, is equivalent to
<b>-n</b>&nbsp;<i>&plusmn;number</i>.
If
<i>number</i>
is not specified in these forms, 10 will be used.
The letter
f
specified as a suffix is equivalent to specifying the
<b>-f</b>
option.
If the
<b>-[</b><i>number</i><b>]c[f]</b>
form is used and neither
<i>number</i>
nor the
f
suffix is specified, it will be interpreted as the
<b>-c&nbsp;10</b>
option.
</blockquote><h4><a name = "tag_001_014_2186">&nbsp;</a>OPERANDS</h4><blockquote>
The following operand is supported:
<dl compact>

<dt><i>file</i><dd>A pathname of an input file.
If no
<i>file</i>
operands are specified,
the standard input will be used.

</dl>
</blockquote><h4><a name = "tag_001_014_2187">&nbsp;</a>STDIN</h4><blockquote>
The standard input will be used only if no
<i>file</i>
operands are specified.
See the INPUT FILES section.
</blockquote><h4><a name = "tag_001_014_2188">&nbsp;</a>INPUT FILES</h4><blockquote>
If the
<b>-c</b>
option is specified, the input file can contain arbitrary
data; otherwise, the input file must be a text file.
</blockquote><h4><a name = "tag_001_014_2189">&nbsp;</a>ENVIRONMENT VARIABLES</h4><blockquote>
The following environment variables affect the execution of
<i>tail</i>:
<dl compact>

<dt><i>LANG</i><dd>Provide a default value for the internationalisation variables
that are unset or null.
If
<i>LANG</i>
is unset or null, the corresponding value from the
implementation-dependent default locale will be used.
If any of the internationalisation variables contains an invalid setting, the
utility will behave as if none of the variables had been defined.

<dt><i>LC_ALL</i><dd>
If set to a non-empty string value,
override the values of all the other internationalisation variables.

<dt><i>LC_CTYPE</i><dd>
Determine the
locale for the interpretation of sequences of bytes of text data as
characters (for example, single- as opposed to multi-byte characters
in arguments and input files).

<dt><i>LC_MESSAGES</i><dd>
Determine the locale that should be used to affect
the format and contents of diagnostic
messages written to standard error.

<dt><i>NLSPATH</i><dd>
Determine the location of message catalogues
for the processing of
<i>LC_MESSAGES .
</i>
</dl>
</blockquote><h4><a name = "tag_001_014_2190">&nbsp;</a>ASYNCHRONOUS EVENTS</h4><blockquote>
Default.
</blockquote><h4><a name = "tag_001_014_2191">&nbsp;</a>STDOUT</h4><blockquote>
The designated portion of the input file will be written to standard output.
</blockquote><h4><a name = "tag_001_014_2192">&nbsp;</a>STDERR</h4><blockquote>
Used only for diagnostic messages.
</blockquote><h4><a name = "tag_001_014_2193">&nbsp;</a>OUTPUT FILES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_001_014_2194">&nbsp;</a>EXTENDED DESCRIPTION</h4><blockquote>
None.
</blockquote><h4><a name = "tag_001_014_2195">&nbsp;</a>EXIT STATUS</h4><blockquote>
The following exit values are returned:
<dl compact>

<dt>0<dd>Successful completion.

<dt>&gt;0<dd>An error occurred.

</dl>
</blockquote><h4><a name = "tag_001_014_2196">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>
Default.
</blockquote><h4><a name = "tag_001_014_2197">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
The
<b>-c</b>
option should be used with caution when the
input is a text file containing multi-byte characters; it may
produce output that does not start on a character boundary.
<p>
Although the input file to
<i>tail</i>
can be any type, the results
might not be what would be expected on some character special
device files or on file types not described by the <b>XSH</b> specification.
Since this specification does not specify the block size used when doing input,
<i>tail</i>
need not read all of the data from devices that
only perform block transfers.
<p>
The
b
suffix in the obsolescent version is not portable outside of
XSI-conformant systems.
</blockquote><h4><a name = "tag_001_014_2198">&nbsp;</a>EXAMPLES</h4><blockquote>
The
<b>-f</b>
option can be used to monitor the growth of a file that is
being written by some other process.
For example, the command:
<p>
<pre>
<code>
tail -f fred
</code>
</pre>
prints the last ten lines of the file
<b>fred</b>,
followed by any lines that are appended to
<b>fred</b>
between the time
<b>tail</b>
is initiated and killed.
As another example, the command:
<pre>
<code>
tail -f -c 15 fred
</code>
</pre>
prints the last 15 bytes of the file
<b>fred</b>,
followed by any bytes that are appended to
<b>fred</b>
between the time
<b>tail</b>
is initiated and killed.
</blockquote><h4><a name = "tag_001_014_2199">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_001_014_2200">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="head.html">head</a></i>.
</blockquote><hr size=2 noshade>
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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